Diagnostic Ultrasound - Abdomen and Pelvis

Diverticulitis
TERMINOLOGY
Definitions
• Diverticulum: Focal sac-like outpouching
• Diverticulosis: Presence of colonic diverticula in absence of
acute signs or symptoms
• Diverticulitis: Inflammation of colonic diverticulum resulting
in clinical signs
IMAGING
General Features
• Best diagnostic clue
○ Evidence of inflammation in thick-walled colonic
segment centered around diverticula
• Location
○ Diverticula
– Can occur anywhere in colon
□ Most common in sigmoid and left colon
• Size
○ Usually 3-5 mm
○ > 4 cm referred to as giant diverticulum
• Morphology
○ Can be solitary or multiple
○ Diverticula
– Herniation of mucosa and submucosa bounded by
thin layer of serosa
□ Referred to as pulsion type or false diverticula
□ Typically at point of weakness where perforating
vessels enter teniae coli
○ Right-sided diverticulum
– Multiple: Pulsion type (false diverticula)
– Solitary: Congenital and true diverticulum; containing
all layers of bowel wall
○ Giant colonic diverticulum
– Congenital (true)
– Acquired (pulsion type with ball valve-type effect)
Ultrasonographic Findings
• Diverticulosis
○ Thickened colon
– Pronounced hypoechoic muscularis propria layer
representing muscular hypertrophy
– Early feature and can precede development of
diverticula; prediverticulosis
○ Diverticula
– Often inconspicuous, masked by gas from overlapping
bowel loops
– Linear echogenic foci with reverberation artifact
protruding out from colonic wall represent gas
– Hypoechoic colonic outpouching with heterogeneous
echogenic foci representing gas and fecalith
• Acute diverticulitis
○ Features of diverticulosis with adjacent inflamed
echogenic pericolic fat
○ Hyperemia on color Doppler assessment
○ Inflamed pericolic fat
– Striking echogenic appearance with localized
tenderness draws operator to underlying abnormality
– Results in localized tenderness and draws operator to
underlying abnormality
– Accentuates hypoechoic muscularis propria and
inflamed diverticula
○ Complications
– Abscess: Loculated fluid collection that may contain
gas and debris
– Fistula: Linear tract outlined by gas or fluid between
thickened colon and adjacent structure
Radiographic Findings
• Giant diverticulum (thin-walled, air-filled structure) may be
incidental finding
CT Findings
• CECT
○ Diverticulosis
– Segmental mural thickening reflecting muscular
hypertrophy and shortening of colon
□ May be seen without diverticula
– Diverticula
□ Focal outpouchings may contain gas, fecalith, or
mixture of both
○ Acute diverticulitis
– Significant pericolonic fat stranding and edema
centered around preexisting colonic diverticulosis
• CTA
○ Performed in cases of acute lower GI bleeding
• CT colonography
○ Diverticulosis/diverticulitis
– 2D: Features overlap with conventional CT
– Impacted fecalith in diverticulum or inverted
diverticulum may mimic polyp
Imaging Recommendations
• Best imaging tool
○ CT is best imaging tool in assessment of acute
diverticulitis, severity, and complications
○ US is valuable in initial assessment of patients with acute
abdominal pain, which includes diverticulitis
○ Typical features on ultrasound are diagnostic of acute,
uncomplicated diverticulitis
○ If US is inconclusive or coexistent complications are
suspected, recommend further imaging with CT
• Protocol advice
○ CT
– Portal-phase CECT with multiplanar assessment
○ US
– Initial overview of abdominal viscera and bowel with
curvilinear probe followed by focused assessment of
bowel using high-resolution linear probe, typically
where maximally tender
– Transvaginal scan can demonstrate features of acute
diverticulitis in pelvic colon
DIFFERENTIAL DIAGNOSIS
Colonic Tumor
• Short-segment colonic mural thickening with destruction of
gut wall layers (gut signature) on ultrasound
• Can be difficult to distinguish from diverticulitis because of
overlapping findings
• Presence of localized mass with pericolonic lymph nodes
favors tumor
Diagnoses: Bowel
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